The advantage of a recirculating automatic document feeder (RADF) is well known in the art. For example, one such advantage is the ability to recirculate a multi-sheet original document, making one copy per circulation, such that the copy output comprises a single stack of many collated copy sets without the necessity of providing an output multi-bin collator.
All known RADF's are bottom feed/top restack devices; that is, the original documents are fed off the bottom of a stack, and rejoin the stack, after copying, by being placed on top of the stack as the stack's topmost sheet. While bottom feeding is more difficult, the prior art inability to bottom stack has necessitated the bottom feed/top restack configuration found in the prior art.
Of course, when recirculation is not provided, it is relatively simple to provide the sheet feeding advantages of top feeding, and this has been done in the prior art.
In addition, it is known that in the broader art of article stacking per se, means such as side-disposed paddle wheels have been used to elevate a stack, and at the same time advance the paddles so as to form a platform for the next article. Thus, as the paddles continue to rotate, and articles continue to be fed, a stack of such articles is formed by bottom feeding.
Another known version of such a stacker per se is that of air-supporting a stack of cards so as to enable the insertion of a card at the bottom of the stack.